While everyone from Zynga on down in our AppData leaderboards saw social gaming traffic drop last month, some got it worse than others. Most obviously, up-and-coming developer CrowdStar grew in the first weeks of the month, when other big developers were leveling off.

Today, CrowdStar is the second-largest Facebook application developer by daily active users, with 10.8 million — behind Zynga’s 62.4 million. While CrowdStar’s DAU count has fluctuated around this number since slightly before Christmas, the cause appears to be players going offline for the holidays. Facebook’s stricter enforcement of anti-viral polices at the beginning of December also appears to have affected CrowdStar less than many other developers.

The company’s growth, meanwhile, is being driven by the fact that its most recent titles are also its biggest ones. While many other developers have big games, most of those games launched many months ago and have already, from what we can tell, reached their traffic peaks.

CrowdStar has developed a wide range of apps in past years, most of which did not prove very popular. But it learned lessons from those efforts, and broke out with Happy Aquarium in September, then followed up with Happy Pets and Happy Island later last fall. It’s not entirely clear what is making the company successful in spite of intense competition and the viral restrictions. Company chairman Peter Relan ascribes the recent growth to focusing on quality games, and on coming out with a new one every month.

Now we’ll get a better chance to see how CrowdStar does versus rivals, post-holidays. Relan says to expect another game later this month. “There are games in genres out there that are goofing around and not really exploring the mechanics,” he threatens. “We’re going to come in there and kick some ass.”